He vowed to get health coverage for the uninsured and to safeguard the environment by capping carbon emissions. He pledged to push for comprehensive immigration reform and help homeowners after the housing market crashed.

Above all, he would change the tenor of the debate in Washington.

"We have a chance to bring the country together in a new majority — to finally tackle problems that Washington has ignored for too long. And that is why the same old Washington textbook campaigns just won't do in this election," he said in Blueprint for Change, a campaign document that became his presidential to-do list.

PolitiFact has been tracking all 508 promises throughout his presidency and keeping tally on the Obameter.

Our scorecard shows Obama kept 37 percent of his promises. He brought the war in Iraq to a close and finally achieved the Democratic dream of a universal health care program. When the United States had Osama bin Laden in its sights, Obama issued the order to kill.

Sixteen percent are rated Promise Broken, often because they hit a brick wall in Congress. Global warming legislation passed the House but died in the Senate. He didn't even push for comprehensive immigration reform. His program to help homeowners facing foreclosure didn't even meet its own benchmarks. (PolitiFact rates campaign promises based on outcomes, not intentions.)

With four months left in Obama's term, PolitiFact has rated Obama's remaining promises Compromise (14 percent), Stalled (10 percent) or In the Works (22 percent).

One stands out as not only his biggest broken promise, but as an explanation for many others that have fizzled or failed: his pledge to bring people together for a bipartisan agenda.

"That, it seems to me, is the most important promise that the president has not been able to keep," said William Galston, a former Clinton administration aide who now is a fellow at the Brookings Institution and studies political polarization. "It will long be debated by historians whether he tried and failed, or didn't really try at all."

This is an accounting of the promises Obama kept and failed to keep, and how bipartisanship eluded him at nearly every turn.

The stimulus

When Obama and Democrats muscled the economic stimulus through Congress in the second month of his presidency, it contained a grab-bag of his promises — tax credits for buyers of hybrid cars, Pell grants for low-income college students and federal dollars for solar, wind and biofuel.

It included Race to the Top, an education grant contest among the states to encourage new testing standards, rewards for good teachers and more emphasis on math and science.

When Obama signed the stimulus into law on Feb. 17, 2009, he said it contained the ideas of both Democrats and Republicans, and it did include a hefty portion of tax cuts.

But the stimulus ended up passing with only three Republican votes in the Senate, and none in the U.S. House of Representatives. The recriminations started.

Republicans blamed Democrats for excluding them from negotiations, said Brian Darling, a senior fellow who studies government at the conservative Heritage Foundation.

"It started out on a bad note," Darling said. "That's when the well was poisoned, very early, during the stimulus debate."

As time went by, Democrats saw the Republican opposition as a purely political tactic: If the stimulus worked, Obama would get credit. If it didn't work, Republicans would be able to throw their opposition back in Obama's face during the next election cycle.

Planned or not, Republicans coalesced into a vocal, unified opposition.

"That became their strategy for the first two years of the Obama administration," noted Jonathan Alter in his book The Promise, a chronicle of Obama's first year in office.

Republicans in Congress weren't Obama's only opponents. Days after the stimulus was signed, CNBC's Rick Santelli gave a commentary on the floor of the Chicago mercantile, slamming Obama's plans to help people facing foreclosures and underwater mortgages.

"How many of you people want to pay for your neighbor's mortgage that has an extra bathroom and can't pay their bills? Raise your hand!" shouted Santelli. The traders surrounding him gave lusty boos.

"President Obama, are you liiiiistening?" he said.

Santelli said he was organizing an event to protest, and he called it a tea party.

Health care and more

When Obama turned to health care, he got a sobering lesson in the ways of Washington.

In the Senate, negotiations started in April 2009 and then dragged on for months, sucking energy and time from Obama's other initiatives. Meanwhile, the White House sacrificed promises on transparency and prescription drugs as it cut deals behind closed doors.

In exchange for concessions from prescription drug makers, Obama abandoned promises to allow imported prescription drugs from Canada, to give Medicare the power to negotiate for cheaper prescription drugs, and to prevent drug companies from blocking generic drugs. And the negotiations did not take place on C-SPAN, as Obama said during the campaign. PolitiFact rated all four pledges Promise Broken.

Still, the final bill was packed with his promises. He earned a Promise Kept on 19 health care pledges, including requiring insurers to cover pre-existing conditions, giving tax credits to help people buy health care, and requiring large employers to contribute to national health care.

But again, the health law proved incredibly divisive. Republicans called it a government takeover of health care and worse, and the partisan lines hardened.

What didn't get done

Obama's success on health care came at a price. He ran out of political capital to spend on other promises.

A cap-and-trade bill to address climate change passed the House, but didn't get a hearing in the Senate. Promises to help labor unions languished. And the administration largely ignored comprehensive immigration legislation, not even pushing to introduce the bill.

"Did Obama say he wanted to pass immigration reform? Yes, often. Did he make it a priority? No," said Frank Sharry, executive director of the pro-immigration group America's Voice.

And Democrats were still coming to grips with the unity and intensity of Republican opposition, Sharry said, and not just on immigration, but on the stimulus and health care.

Democrats had expected Republicans to be chastened after the 2008 elections and willing to compromise. But compromise never happened.

"The way the Republicans organized to say no to everything, the way they did it so ruthlessly and effectively, it was just mind-boggling," he said.

GOP takes the House

The election in November 2010 brought Republicans back to power in the House, with strong support from the tea party movement.

Afterward, Obama managed to hammer out a rare compromise with Republicans and Democrats. They agreed to postpone the expiration of a series of tax cuts passed under President George W. Bush that were due to expire at the end of the year.

That agreement allowed Obama to fulfill promises not to raise taxes on families who made less than $250,000. But it also meant he broke his promise to raise taxes on the wealthy.

Even as Obama won the moment of compromise, he compared his negotiating partners with hostage-takers.

"I think it's tempting not to negotiate with hostage-takers, unless the hostage gets harmed," Obama said. "In this case, the hostage was the American people and I was not willing to see them get harmed."

When the new Congress convened in 2011, almost everything on Obama's wish list that required legislative approval came to a grinding halt.

In addition to domestic policy, Congress kept the brakes on some of Obama's foreign policy initiatives. Most notably, Guantanamo Bay — the detention center for terrorism suspects that Obama wanted closed — stayed open. We rated Obama's pledge to close it Promise Broken.

And prospects for bipartisan compromise were raised and then dashed during the battle over the debt ceiling.

Republicans wanted spending cuts in return for what in years past had been a largely symbolic vote. Budget negotiations continued right up to the last minute, finally coming to a conclusion on Aug. 2, 2011, when the two sides formally agreed to punt budget cuts to a super-committee.

In the meantime, the United States received a historic downgrading of its credit from Standard & Poor's. Then the super-committee failed, too. Looming for 2013: automatic, across-the-board spending cuts (called sequestration) that neither side really wanted in the first place.

As the 2012 election has approached, Congress has turned away from law-making and toward campaigning. Obama no longer speaks of bringing Democrats and Republicans together to pass an agenda. PolitiFact rated that Promise Broken.

Back in 2004, Obama famously said, "There's not a liberal America and a conservative America; there's the United States of America."

He doesn't say anything like that today.

In a campaign ad, Obama sits alone in a room. He looks directly at the camera and goes through his overarching policy ideas. He wants to raise taxes on the wealthy to pay for investments in education, energy and manufacturing, just as he promised in 2008.

This time, there's no talk of bipartisanship.

"It's a choice," he says, "between two very different plans for our country."

Democratic National Convention

When: Tuesday-Thursday.

Where: Charlotte, N.C. The first two days will be at the Time Warner Cable Arena. President Barack Obama and Vice President Joe Biden will accept their nominations Thursday at Bank of America Stadium.

PolitiFact is tracking 508 promises made by Barack Obama in the 2008 presidential campaign. Here's the tally so far:

Promise Kept: 190 (37 percent)

Compromise: 72 (14 percent)

Promise Broken: 83 (16 percent)

Stalled: 49 (10 percent)

In the Works: 112 (22 percent)

Not yet rated: 2 (0 percent)

Note: Percentages don't add up to 100 because of rounding.

Top 10 Promises Broken (so far)

1Create a foreclosure prevention fund for homeowners.What happened? Obama created a fund, but it failed to meet its own benchmarks for helping homeowners. A special inspector general deemed the program "a colossal failure."

2 Repeal the Bush tax cuts for higher incomes.What happened? In 2010, Obama agreed to a deal with Republicans to extend the current tax rates for another two years. Obama will get another shot at keeping this promise if he wins re-election.

3 Close the Guantanamo Bay Detention Center.What happened? Obama has consistently said he wants the facility closed, but he hasn't found a way to get Congress to agree. Guantanamo Bay remains open.

What happened? A bill for cap-and-trade passed the U.S. House of Representatives in 2009, but the Senate wouldn't bite. Now Republicans control Congress, and it's considered dead.

5 Sign the Employee Free Choice Act, making it easier for workers to unionize.

What happened? This didn't get done when Democrats controlled Congress, and now it looks as if it won't get done at all, thanks to Republican opposition.

6 Allow imported prescription drugs.What happened? The White House dropped this pledge as it lured drugmakers to get on board with the president's health care law. The promise hasn't been heard from since.

7 Sign the Freedom of Choice Act.What happened? Candidate Obama said one of the first things he wanted to do was sign abortion rights legislation. President Obama said he had other priorities and wanted to tamp down anger surrounding the issue.

8 Create a public option health plan for a new National Health Insurance Exchange.

What happened? Congress rejected the idea for a public health insurance option open to everyone. Obama downplayed the fact that it was left out of the final version of the health care law.

9 Introduce a comprehensive immigration bill in the first year.What happened? Obama said he would introduce legislation that included a path to citizenship for illegal immigrants. But other priorities — health care and financial regulation — seemed to run out the clock.

10 Bring Democrats and Republicans together to pass an agenda.What happened? On matters large and small, partisanship is worse than ever.

Top 10 Promises Kept (so far)

1 End the use of torture.What happened? Obama said he would stop the torture of terror suspects, and human rights experts say he did.

2 Seek verifiable reductions in nuclear stockpiles.What happened? In 2010, the Senate ratified a new START treaty for the United States and Russia to verify reductions in nuclear weapons.

3 Create new financial regulations.What happened? Obama signed a massive overhaul of financial regulations in 2010. It included a new Consumer Financial Protection Bureau to look out for the little guy.

4 Sign a "universal" health care bill.What happened? Republicans may hate the individual mandate, but it allows Obama to make a credible case that the health care law will lead to universal coverage.

5 Extend the Bush tax cuts for lower incomes.What happened? A rare compromise with Republicans at the end of 2010 left in place current tax rates for middle-class Americans. What happens when they expire in 2013 is the great unknown.

6 Fully fund the Veterans Administration.What happened? It doesn't get much attention, but Obama kept his promises on veterans, sending more money and resources to programs that serve them.

7 Direct military leaders to end war in Iraq.What happened? Obama did as he said, bringing the Iraq war to its conclusion. A Promise Kept for a huge campaign issue.

8 Repeal "Don't Ask, Don't Tell" policy.What happened? The policy that stopped gays and lesbians from serving openly in the military ended in 2011.

10 We will kill bin Laden.What happened? On the campaign trail, Obama said the United States would go after Osama bin Laden if it got the chance. When U.S. forces found the terrorist in Pakistan, they took him out.